Present OSHA enforced federal decompression schedules for compressed air and caisson workers produce a 33% incidence of aseptic necrosis at pressures over 36 pounds and an unacceptable incidence of decompression sickness at lower pressures. A new set of interim decompression tables has been computer generated using the Autodec computer system which has gained acceptance and use in the commercial diving field. The present OSHA tables will be analyzed using whole body nitrogen wash-out studied to determine the amount of residual nitrogen present after decompression. These nitrogen wash-outs will then be compared with similar studies carried out on the same subjects using the new interim tables. During decompression and following decompression, ultra-sonic tissue imaging of selected body tissues will be used to quantitate stationary bubble formation in the body during decompression and following decompression on both the new and the old tables. Modifications will be made in decompression profiles and lengths of stop as required to minimize gross bubble formation. These modifications will be made based on whole body nitrogen wash-out data and quantitative bubble counting using ultra-sonic tissue imaging. We are about to embark on the second year of a proposed three year contract to test and modify the interim tables.